Stochastically Perturbed Parmaters [SPP]

Andrew Singleton

Preliminary point verification for SOP 1

What parameters do we perturb?

  • Cloud thickness threshold for shallow / deep convection
  • Cloud ice content impact on cloud thickness
  • Ice nucleii concentration
  • Saturation limit sensitivity for condensation*
  • Kogan autoconversion speed
  • Kogan sub grid scale (cloud fraction) sensitivity*
  • Impact of graupel on radiation
  • Impact of snow on radiation*
  • Top entrainment efficiency
  • Stable conditions length scale
  • Asymptotic free atmosphere length scale

However… This Presentation is not as advertised!

  • Original reference runs had problems with warm perturbed members in winter and dry perturbed members in summer
  • Original reference did not include modelling of snow on sea ice
  • Some default physics parameter values are changed for SPP
  • The reference is re-run with
    • 6 perturbed members
    • No surface data assimilation for perturbed members
    • Snow on sea ice modelling
    • Physics parameter defaults changed

Point verification for (near) surface parameters

2m Temperature

2m Temperature [members]

2m Temperature “first guess”

Temperature [upper air]

2m Humidity

2m Humidity [members]

Relative Humidity [upper air]

10m Wind Speed

10m Wind Speed [members]

Wind Speed [upper air]

6h Precipitation

6h Precipitation [members]

Total Cloud Cover

Total Cloud Cover [members]

Geopotential Height [upper air]

Summary

  • Warming of perturbed members reduced
  • Night time wet bias removed in perturbed members
  • Large positive bias in initial cloud cover for perturbed members removed
  • Overall reduction in spread for all parameters
  • Less spread throughout atmosphere